Thin air / the greek crash

I am not a pilot, and as much as my email address sounds like I am a
doctor, I'm not...

That said, I thought someone here might be able to help me out - they
news reports talk about passing out within seconds at high altitudes.
I understand the air is thinner / less O2.

But if I go underwater, there's certainly no air there. And I can stay
down for a while, holding my breath. How is high altitudes different?
I would think you would rasp / fight to breath in but keep functioning
as your body uses up the 02 in the blood from your last breath? Not
like a sleeping gas in the movies where you just keel over as soon as
it hits you?

THANKS!

Stolen off the net...

Hypoxia

Hypoxia is a deficiency of oxygen which impairs the brain functions
and other organs. As we gain altitude, the atmosphere decreases in
pressure. Although the air still is 21 percent oxygen, the amount of
oxygen present also is decreased as the air pressure is decreased.

Night vision begins to deteriorate at about 5,000 feet MSL. From about
12,000 to 15,000 feet MSL, judgment, memory, alertness, coordination,
and ability to make calculations are impaired. Some pilots might feel
dizzy or drowsy. A sense of well-being (euphoria) or belligerence can
occur. A pilot's performance can seriously deteriorate within 15
minutes at 15,000 feet MSL. Above 15,000 feet MSL, the periphery of the
visual field grays out to a point where only central vision remains
(tunnel vision). Fingernails and lips turn blue. The ability to take
corrective and protective action is lost in 20 to 30 minutes at 18, 000
feet and 5 to 12 minutes at 20,000 feet MSL, followed soon thereafter
by unconsciousness.

The effect of hypoxia occurs at lower altitudes with the use of some
medication, smoking, alcohol, emotional stress, etc. The worst part is
the fact that hypoxia is very difficult to recognize because of the
gradual dulling of the senses. Since symptoms of hypoxia do not vary in
an individual, the ability to recognize hypoxia can be greatly improved
by experiencing and witnessing the effects of it during an altitude
chamber "flight." The FAA provides this opportunity through
aviation physiology training, which is conducted at the FAA Civil
Aeromedical Institute (CAMI) and at many military facilities across the
United States. To attend the Physiological Training Program at CAMI
telephone (405) 954-6212 or write:

Mike Monroney Aeronautical Center
Airman Education Program Branch
AAM-420 CAMI
P.O. Box 25082
Oklahoma City, OK 73125

Low ambient air pressure on the outside of your body compared to the higher
pressure inside your body makes gasses on the inside want to get out.

I am not a pilot, and as much as my email address sounds like I am a
doctor, I'm not...

That said, I thought someone here might be able to help me out - they
news reports talk about passing out within seconds at high altitudes.
I understand the air is thinner / less O2.

But if I go underwater, there's certainly no air there. And I can stay
down for a while, holding my breath. How is high altitudes different?
I would think you would rasp / fight to breath in but keep functioning
as your body uses up the 02 in the blood from your last breath? Not
like a sleeping gas in the movies where you just keel over as soon as
it hits you?

THANKS!

wrote:
I am not a pilot, and as much as my email address sounds like I am a
doctor, I'm not...

That said, I thought someone here might be able to help me out - they
news reports talk about passing out within seconds at high altitudes.
I understand the air is thinner / less O2.

But if I go underwater, there's certainly no air there. And I can stay
down for a while, holding my breath. How is high altitudes different?
I would think you would rasp / fight to breath in but keep functioning
as your body uses up the 02 in the blood from your last breath? Not
like a sleeping gas in the movies where you just keel over as soon as
it hits you?

As others have posted in the other thread, it is all about pressures.
As you go up in altitude, pressures decrease, so gases come out of
solution (blood).
As you go deeper beneath the surface of the water, the pressure
increases, trapping gases in solution (blood).

The term that you would want to research is "Time of Useful
Consciousness (TUC)"... If it is a gradual pressure loss, you might not
realize it and basically just drift off to sleep...

Tlme of useful
consciousness
Altitude (ft) without oxygen

40,000 15 seconds
35.000 20 seconds
30,000 30 seconds
28,000 1 minute
26,000 2 minutes
24,000 3 minutes
22,000 6 minutes
20,000 10 minutes
15.000 Indefinite

Source: "Physiologically Tolerable Decompression Profiles for
Supersonic Transport Type Certification," Office of Aviation Medicine
Report AM' 70-12, S. R. Mohler, M.D., Washington, D.C.; Federal
Aviation Administration, July 1970.

One thing from the AP story that probably needs correcting is the
statement that "you can stay awake longer at 10,000 feet". This comment
was made by an F-16 pilot following the doomed airliner. While I'm sure
he wears O2 at 10,000 feet, most of us can continue to function very
well at 10,000 feet for extended periods of time. Although I carry O2,
I don't usually put it on until 12,000 feet. However, the effect of
altitude happens quickly as you climb. Of course the problem with
extream altitudes like those taht airlines fly at is that the O2 is
"sucked" out of your system by the enourmous pressures. You really only
have seconds to put on your quick dawn masks. It will be interesting to
see if the black box indicates why the pilots were not able to put on
their masks. In the US, pilots are taught to put on the O2 mask ASAP
and then fly the plane second. You can loss conscience pretty fast.
This type of thing has happened to US airliners without serious
outcomes because the pilots put on their masks right away. It will be
interesting to see what made that not happen in this case.
BTW: There are indications that the captain was not in the cabin at the
time. In the US the pilot in the cockpit is required to wear his O2
mask if the other pilot steps out for a potty break.

-Robert, CFI

"Robert M. Gary" wrote
In the US the pilot in the cockpit is required to wear his O2
mask if the other pilot steps out for a potty break.

But...in my 25 years of airline flying including jumpseat riding
on many US carriers, this is not very often done.

Bob

"Robert M. Gary" writes:
In the US, pilots are taught to put on the O2 mask ASAP
and then fly the plane second. You can loss conscience pretty fast.
This type of thing has happened to US airliners without serious
outcomes because the pilots put on their masks right away. It will be
interesting to see what made that not happen in this case.

To quote the front page article in the New York Times:

"The two Greek fighter pilots who shadowed the passenger plane
spotted the co-pilot slouched over the controls. He was wearing an
oxygen mask, apparently unconscious, Greece's government
spokesman, Theodore Roussopoulos, said after a marathon crisis
meeting led by the Greek prime minister."

If this is an accurate observation, then failing to put on the oxygen
mask was not the problem.

Chris
--
Chris Colohan Email: PGP: finger
Web: www.colohan.com Phone: (412)268-4751

In article .com,
"Robert M. Gary" wrote:

You can loss conscience pretty fast.

Nice verbal glitch there . . . lots of things besides thin air can cause
loss of conscience.

"Chris Colohan" wrote in message
.. .
"Robert M. Gary" writes:
In the US, pilots are taught to put on the O2 mask ASAP
and then fly the plane second. You can loss conscience pretty fast.
This type of thing has happened to US airliners without serious
outcomes because the pilots put on their masks right away. It will be
interesting to see what made that not happen in this case.

To quote the front page article in the New York Times:

"The two Greek fighter pilots who shadowed the passenger plane
spotted the co-pilot slouched over the controls. He was wearing an
oxygen mask, apparently unconscious, Greece's government
spokesman, Theodore Roussopoulos, said after a marathon crisis
meeting led by the Greek prime minister."

If this is an accurate observation, then failing to put on the oxygen
mask was not the problem.

Chris
--


Contamination of the pilots O2 supply?